An UObject is created by the K2Node_ custom node then the K2 uses KismetCompiler utilities to copy the generated UFunction from that UObject, spawn that “node” (invisible) onto the Ubergraph, move it’s own connections from generated pins into the spawned node, detach itself to not be called twice and then let the Blueprint Graph do its job executing the “generated” node.
Later the UObject is GCed if there’s no more K2Node_ referencing him anymore (Kismet Compiler has no use to it anymore so it’s garbage collected).
It’s the same thing all Blueprint Nodes behind the scenes in runtime…
I’m building my own IntelliSense tech.
I call it IntelliNonsense™